Applicant's co-owned U.S. Pat. No. 4,927,125 discloses a set-up assembly with upper and lower plates hingedly connectable and disconnectable along two spaced parallel axes. Applicant expressly incorporates U.S. Pat. No. 4,927,125 by reference herein, in its entirety. Aligned with each axis, the set-up assembly includes a pair of axially extendable and retractable center pins mounted on one of the plates which may be quickly and easily moved along the axis into and out of engagement with the other plate. The use of extendable and retractable center pins to accurately hold the upper plate to the lower plate simplifies set up operations and reduces the operator's set-up time for those machining operations which require hinged raising of either end of the upper plate.
The extendable and retractable center pins also facilitate machining operations which require simple, fast and effective holding of a pallet to a support plate. With a plurality of pallets, a workpiece mounted to each pallet, and a machining device located adjacent a lower plate in an operating position, the workpiece-holding pallets can be connected and disconnected to the lower plate in assembly line fashion to reduce machining time and expense.
With this set up assembly, the center pins are spring-biased inwardly toward the pallet. To retract the pins, the pins are pulled outwardly against the spring force and then rotated perpendicularly into a latched position. For larger size plates, i.e., ten inches by twelve inches, the spring force is generally much higher, so that the upper plate can be held securely in position for machining operations. Unfortunately, for upper plates of this size, the high spring force makes it difficult to manually retract the pins outwardly from engagement.
Moreover, because of the structural relationship of the pin, the spring and the lower plate, this structure does not lend itself particularly well to automated placement, securement and removal of the upper plate to a workstation. This is due primarily to the susceptibility of pin or pin component breakage if the pin is retracted too far or rotated at the wrong time.